Invading my space

My step son is 15 and at times has been "invading my space." As he walks by, he might slide his hand across my shoulder or arm or leg or back. My reaction has been to tell him, "Do you want to keep that arm?" and I am not talking in a joking way. I know he knows I'm serious and that I do not want him to touch me like that. His dad thinks it's funny.